Field of the Invention
This invention is directed to the synthesis of deoxycholic acid and salts thereof as wed as to intermediates useful in the synthesis of deoxycholic acid. In one embodiment, this invention provides synthetic methods for preparing deoxycholic acid or a salt thereof starting from hydrocortisone. This invention is also directed to intermediates such as 12-keto or 12-α-hydroxysteroids as well as novel processes for their preparation. This invention still further provides purified deoxycholic acid compositions and methods for purification wherein the deoxycholic acid has a purity of at least 96%.
State of the Art
Rapid removal of body fast is an age-old ideal, and many substances have been claimed to accomplish such results, although few have shown results. “Mesotherapy”, or the use of injectables for the removal of fat, is not widely accepted among medical practitioners due to safety and efficacy concerns, although homeopathic and cosmetic claims have been made since the 1950's. Mesotherapy was originally conceived in Europe as a method of utilizing cutaneous injections containing a mixture of compounds for the treatment of local medical and cosmetic conditions. Although mesotherapy was traditionally employed for pain relief, its cosmetic applications, particularly fat and cellulite removal, have recently received attention in the United States. One such reported treatment for localized fat reduction, which was popularized in Brazil and uses injections of phosphatidylcholine, has been erroneously considered synonymous with mesotherapy. Despite its attraction as a purported “fat-dissolving” injection, there is little safety and efficacy data of these cosmetic treatments. See, Rotunda, A. M. and M. Kolodney, Dermatologic Surgery 32: 465-480 (2006) (“Mesotherapy and Phosphatidylcholine Injections: Historical Clarification and Review”).
Recently published literature reports that the bile acid, deoxycholic acid, and salts thereof, have fat removing properties when injected into fatty deposits in vivo. See, WO 2005/117900 and WO 2005/112942, as well as US2005/0261258; US2005/0267080; US2006/127468; and US200601549062, all incorporated herein by reference in their entirety). Deoxycholate injected into fat tissue degrades fat cells via a cytolytic mechanism. Because deoxycholate injected into fat is rapidly inactivated by exposure to protein and then rapidly returns to the intestinal contents, its effects are spatially contained. As a result of this attenuation effect that confers clinical safety, fat removal therapies typically require 4-6 sessions. This localized fat removal without the need for surgery is beneficial not only for therapeutic treatment relating to pathological localized fat deposits (e.g., dyslipidemias incident to medical intervention in the treatment of HIV), but also for cosmetic fat removal without the attendant risk inherent in surgery (e.g., liposuction). See, Rotunda et al., Dermatol. Surgery 30: 1001-1008 (2004) (“Detergent effects of sodium deoxycholate are a major feature of an injectable phosphatidylcholine formulation used for localized fat dissolution”) and Rotunda et al., J. Am. Acad. Dermatol. (2005: 973-978) (“Lipomas treated with subcutaneous deoxycholate injections”), both incorporated herein by reference in their entirety.
In addition, many important steroids have a 12-α-hydroxy-substituent on the C-ring of the steroid. Such compounds include, by way of example, bile acids such as deoxycholic acid, cholic acid, lithocholic acid, and the like. Heretofore, such compounds were typically recovered from bovine and ovine sources which provided a ready source of bile acids on a cost effective basis. However, with the recent discovery that pathogens such as prions can contaminate such sources, alternative methods for the synthesis of bile acids from plant sources or synthetic starting materials have become increasingly important. For example, deoxycholic acid from animals in New Zealand are a source of bile acids for human use under US regulatory regimes, as long as the animals continue to remain isolated and otherwise free of observable pathogens. Such stringent conditions impose a limitation on the amount of suitable mammalian sourced bile acids and does not preclude the possibility that the bile acid will be free of such pathogens.
There remains a need for suitable quantities of efficacious bile acids such as deoxycholic acid that are known from the outset to be free from moieties of animal origin (or pathogenic moieties capable of acting in an animal, particularly a mammal, and for human use, having a deleterious effect on a human), and other harmful agents such as animal or microbial metabolites, toxins, including bacterial toxins, such as pyrogens, for use as medicaments in humans.
In addition, there is a need to prepare a bile acid composition free of other unintended bile acids. In this regard, it is known that mammalian sourced deoxycholic acid is contaminated with cholic acid. In turn, it is further known that cholic acid is an essential component in the formation of gall atones. Accordingly, there is an ongoing need to provide methods for preparing deoxycholic acid which methods would not result in contamination with other bile acids.
Heretofore, GB2452358 discloses the synthesis of deoxycholic acid starting with 9α-hydroxyandrost-4-en-3,17-dione. In that synthesis, the intermediate 3α-hydroxy-5β-androst-9(11)-en-17-one is disclosed as being derived from 9α-hydroxyandrost-4-en-3,17-dione. While 9α-hydroxyandrost-4-en-3,17-dione is effectively converted to deoxycholic acid as disclosed in that patent, synthesis of deoxycholic acid from hydrocortisone would be of particular value as hydrocortisone is widely available.
Cortisone and hydrocortisone have an 11-keto or 11-β-hydroxy group respectively rather than the 12-α-hydroxy group of deoxycholic acid. Conversion of the 11-keto or 11-β-hydroxy group on the steroidal backbone to the corresponding 12-α-hydroxy or 12-keto group is non-trivial as not only must the conversion be made it must be made stereoselectively. International Patent Application Publication No. WO2008/157635 reports multiple reaction schemes where, in one instance, a 3-β-acetoxy-11-keto steroid is converted to a 3-β-acetoxy-12-α-hydroxysteroid via formation of a Δ-9,11-ene functionality in said steroid following by allylic oxidation at the 12-position with chromium trioxide. The use of chromium trioxide provides modest yields of the Δ-9,11-ene-12-oxo functionalities and side products generated by this reaction encumber purification of the desired product. Moreover, chromium trioxide is highly toxic, corrosive, and carcinogenic. It is the main example of hexavalent chromium, an environmental hazard. Use of chromium trioxide in the oxidation process should be limited.
In view of the above, there is a need to provide a synthetically efficient method for converting 11-β-hydroxy/11-keto steroids to the corresponding a Δ-9,11-ene, 12-α-hydroxy/12-keto steroids using environmentally compatible and less toxic oxidizing agents.
Pharmaceutical grade chemicals require consistently reproducible levels of purity. In some embodiments, purification processes should provide at least 95% purity or at least 99% purity. However, purification to at least 99% is technically challenging. For example, solvents used in the purification process can become entrapped with the product thereby reducing its purity and other contaminants can be carried over by any purification process.
This problem is particularly relevant with deoxycholic acid and salts thereof as this product is disclosed for cosmetic use in removing undesirable fat deposits. See, e.g., U.S. Pat. No. 7,622,130 which is incorporated herein by reference in its entirety. As cosmetic procedures are entirely elective, higher safety standards are typically required by regulatory authorities.